Small RNAs in transcriptional gene silencing and genome defence

Small RNA molecules of about 20 - 30 nucleotides have emerged as powerful regulators of gene expression and genome stability. Studies in fission yeast and multicellular organisms suggest that effector complexes, directed by small RNAs, target nascent chromatin- bound non- coding RNAs and recruit chromatin modifying complexes. Interactions between small RNAs and nascent non- coding transcripts thus reveal a new mechanism for targeting chromatin- modifying complexes to specific chromosome regions and suggest possibilities for how the resultant chromatin states may be inherited during the process of chromosome duplication.